Some of these tools trick your device into believing they are on your trusted network. Example of this is the WiFi Pineapple (the wifi-vpn.com team has used this in demonstrations before) It uses a simple software called Jasager "Yes Man" that causes your device (smartphone, laptop, etc..) to think it is connected to your existing wifi networks, like your home wifi. Once connected anyone who controls the device can sniff all traffic.

These systems can be thwarted by the use of a vpn. WiFi-VPN allows you to connect to our secure servers and keep your traffic safe. For $99 a year this is a small price to pay for security.